Coronaviruses are large, enveloped, single-strand RNA viruses that cause respiratory and/or enteric disease in mammals and birds (18). In dogs, three coronaviruses have been described so far. Canine coronavirus (CCoV) type I and type II are enteric viruses belonging to the antigenic group 1 (13), whereas canine respiratory coronavirus (CRCoV), first reported in UK by Erles et al. (19), is a group-2 coronavirus causing respiratory distress especially when associated to other pathogens (1, 9).
Type I and II CCoVs are widely distributed in Europe (7, 14) and are usually responsible for the appearance of mild to moderate gastroenteritis in pups, although death can occur as a consequence of simultaneous infections by both genotypes (5) or by other pathogens (3-11). Single CCoV infections are restricted generally to the gastroenteric tract, leading to the appearance of anorexia, diarrhoea and vomiting (Tennant et al., 1991).
Because of the widespread infections associated with CCoV, a need exists for vaccines capable of protecting against CCoV infections in canines.